1. Field of the Invention
This invention relates to apparatus and methods for spacing polyvinyl chloride materials or other synthetic plastic materials to prevent accelerated deterioration due to exposure to solar radiant energy and the like.
2. Prior Art Relating to the Disclosure
Polyvinyl chloride (PVC) materials are extemely versatile in the sense that, by varying the amount of plasticizers added to the material, a wide range of characteristics can be obtained. For example, a polyvinyl chloride material with no plasticizers is used for rigid pipes and the like. Addition of appropriate plasticizers to a polyvinyl chloride material produces a material which can be formed into thin, flexible sheets. Both the rigid pipe and the flexible sheets are used, as described in U.S. Pat. No. 4,136,408, to provide a lightweight removable cover for a pool, greenhouse, or the like. Tubular rigid polyvinyl chloride pipes are joined together to provide a rigid support frame for the flexible polyvinyl chloride cover sheet which overlies the frame and covers the enclosure thereby defined. Heretofore, the flexible sheet polyvinyl chloride material directly contacted the rigid polyvinyl tubular support members and was clamped at its lower ends to the vertical side walls of the structure. This structure and method of assembly have proved entirely satisfactory for enclosures of this type. However, after these structures are exposed to strong sunlight for a period of time, the clear, flexible polyvinyl chloride sheet material overlying and directly contacting the rigid polyvinyl chloride support structure discolors and deteriorates at an accelerated rate in comparison to areas of the flexible sheet which are not in contact with the support members. The sheet material overlying the support members gradually becomes brittle and cracks. The flexible polyvinyl chloride sheet material also fuses to the rigid polyvinyl chloride pipe due to heat buildup between the sheet and the supporting pipe. This accelerated deterioration of the flexible polyvinyl chloride material in contact with the polyvinyl chloride material due to exposure to sunlight is a serious problem and detracts from the appearance and utility of enclosures constructed from the otherwise very satisfactory materials.